If the front edge of a crimped shotshell is hitting your forcing cone, your shells are too long and what you're doing can be quite dangerous. The shell is supposed to fit the chamber after it's fired and the crimp is opened. If the crimp is opening into the forcing cone, you could have a very bad day.
A 2-3/4" shotshell with star crimp for example is 2-3/4" when fired and the crimp is open. When crimped they're usually around 2-1/4".
A roll crimped shotshell, when crimped, is sometimes longer, sometimes shorter, sometimes the same length but still should not exceed 2-3/4" when fired and the crimp is opened.
Sometimes a crimp will open very slightly into the forcing cone. I've talked to a couple people who shoot 2-3/4" shells in 2-5/8" chambered shotguns without issue but we're talking about 1/8" possibly ending up in the forcing cone. If the entire crimp was opening into the forcing cone, or worse, part of the crimped shell was being forced into the forcing cone, you could split your barrel and possibly seriously injure or kill yourself.
